Mold inhibitive cellulosic structure



Patented Apr. 14, 1942 MOLD INHIBITIVE CELLULOSIC STRUCTURE Walter John Jebens, Kenmore, N. Y.', assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing.

Application February 21, 1939,

Serial No. 257,586

' 16 Claims.

This invention relates to non-fibrous, transparent, cellulosic wrapping tissue which is coated with a moisture-proofing coating composition having mold inhibitive properties.

In recent years films and foils of regenerated cellulose which have been coated with a lacquer to impart moistureproofness, which foils are extremely transparent and possess a surface of high luster and agreeable appearance, have found favor for wrapping a large variety of materials and articles in order to protect them from con tamination, and in certain instances, to maintain the moisture content of the article or material at some optimum value. These wrapping tissues, being transparent, afford a view of the object which aids greatly in its appeal and sales value.

It has been observed, however, that this wrapping material is often subject to unsightly mold growth which greatly detracts from the appeal of the package. This is particularly evident in certain instances where the article wrapped is of high moisture content and is apt to be infected with mold spores. This, for instance, has been observed in the case of cigars wrapped in regenerated cellulose film which is provided with the usual moistureproofing coating composition of the type disclosed in the Charch and Prindle U. S. Patent No. 1,737,187.

It is an object of this invention to produce a non-fibrous, transparent, moistureproof, cellulosic pellicle which is not subject to mold growth.

It is another object of this invention to produce a non-fibrous, transparent, moistureproof,

cellulosic pellicle containing a mold inhibiting substance in the mositureproofing coating.

It is a further object of this invention to provide a moistureproofing composition which can be used for the production of a transparent pellicle and which contains a material capable of inhibiting mold growth on the pellicle.

Other objects of the invention will appear here inafter.

Attempts have been made, heretofore, to produce a non-fibrous, transparent, cellulosic wrapping tissue, coated with a moistureproofing composition, which will be free from mold growth. The criteria for materials which will prevent mold on such cellulosic material are so precise that as a general rule, previously known fungicides and microbicides could not be satisfactorily used for this purpose. A mold inhibiting material to be satisfactory for preventing mold on cellulosic materials of the type mentioned, must have the following characteristics:

(1) It must not be toxic, even when in long direct contact with foodstuffs. Y

(2) It must have no odor.

(3) It must be capable of functioning in such very small amounts as will not interfere with the transparency of the wrapping tissue.

(4) It must not interfere with the moistureproofness of the coating.

(5) It must not interfere with the heat sealability of the coated tissue.

In view of these very exacting conditions the incorporation in a non-fibrous, transparent, cellulosic wrapping tissue of a material which will satisfactorily inhibit mold growth presents a special problem.

It has now been found that the objects of the invention may be accomplished by coating a nonfibrous, transparent, cellulosic pelliclewith a moistureproofing lacquer comprising a small amount of an alkyl, aryl or alkyl-aryl derivative of thiuram mono-sulfide or thiuram di-sulfide.

Smooth, transparent films of regenerated cellulose or similar water-sensitive, non-fibrous, transparent, cellulosic films, containing from 10% to 20% of glycerol as a softener, or any one of a number of materials well known to provide flexibility and durability in such cellulosic structures, is coated by any one of the mean well known in the art such as by dipping and smoothing with doctor knives, spraying or brushing with a solution which comprises, in general, a moistureproofing agent (such as a wax), a film-forming agent, such as a cellulose derivative, a resin serving as a blending agent for the wax and the cellulose derivative, and a plasticizer to render the coating flexible, together with a small proportion of the sulfide agent hereinafter described. These coating compositions may be applied from a solvent or a mixture of solvents as described in the Charch' and Prindle patent referred to above. The materials which have been found useful to inhibit mold growth upon transparent pellicles f coated with moistureproofing compositions of the kind referred to have the following structural formula:

in which R1, R2, R3, and R4, may be hydrogen,

alkyl or aryl groups, and a: may be either 1 or 2.

methyl thiuram di-suifide. Since these materials are soluble in the solvents used in the moistureproofing coating compositions, they may be added directly to these compositions before application of the latter to the film surface. It has been found that only small amounts need be added to the coating composition, for example, from 0.1% to 1.0% of the lacquer solids and preferably from 0.3% to 0.5%. When it is considered that the coating on a pellicle is of the order of about 0.0001" in thickness. it is truly remarkable that the presence of the minute amount of i the sulfide will very materially inhibit mold.

growth. a

The following examples will aid in an understanding of the invention. although they are to be taken as illustrative and not limitative thereli'rciiinple I A transparent sheetof regenerated cellulose of a thickness suitablefor wrapping tissue and containing of glycerol and 6% of water, based upon the weight' of the cellulose,- is passed through a bath with the following composition:

After passing. through the bath, excess liquid is scraped from the surface of the sheet, smoothed,

and the solvents evaporated. The film so obtained is found to show excellent transparency and moistureproofness, and to give a very tight seal when subjected to heat and pressure, entirely suitable for use in wrapping cigars and to be extremely resistant to the growth of mold. Furthermore, such film has no undesirable toxic effect nor undesirable odor and, hence, is suitable for use as wrapping tissue for cigars, foodstuffs, toilet articles, etc.

Example 11 Regenerated cellulose film as in Example I is" coated with the following composition:

Example III Regenerated cellulose film was coated with the following formula: 1

awe

Example 1V Regenerated cellulose film as in Example I was coated with the following composition:

, -Per cent 12.0% N: 15 sec. nitrocellulose; 6.50 Ester gum- 2.88 Dibutyl phthalate 4.30 Paraflln 0.40 Tetrabutyl thiuram di-sulfide 0.12 Alcohol 2.10 Ethyl aceta 47.00 Toluene. 36.70

with the compositions of Examples 11, III andIV -were found to have the desirable properties of Example I.

. Per cent 12.0% N: 15 sec. nitrocellulose 6.50 Ester gum' 2.93 Dibutyl phthalate 4.30 Paraffin 0.40 Tetraethyl thiuram dl-sulfide 0.07 Alcohol 2.10 Ethyl acetate 47.00 Toluene 36.70

Per cent 12.5% N; 10 sec. nitrocellulose 6.70 Damar res 1.75 Parailln 0.50 Dibutyl phthalate 2.80 Tetramethyl thiuram mono-sulfide 0.05 Alcohol 3.00v Ethyl acetate 51.00 Toluene 34.20

Films prepared according to the above examples are found to exhibit, either none or a negligible amount of mold even after storage for three months at a temperature of 104 F. and" at a relative humidity of Although the tetramethyl and tetraethyl derivatives of mono-' and di-sulfides have been found to be particularly useful in accordance with the present'invention, other 'alkyl, aryl, and

'alkyl-aryl derivatives of thiuram sulfides have been found to be'operative. As further examples of such other derivatives of thiuram monoand di-sulfide which may be used in accordance with the present invention, the following, may be mentioned: tetrabutyl thiuram di-sulfide, tetra ethyl thiuram di-sulfide, diethyl dimethyl thiuram di-sulflde, dicyolopentyl methylene thiuram di-sulfide, dicyclopentyl methylene thiuram mono-sulfide, ferric dimethyl dithiocarbamate. The thiuram'sulfides may in fact contain, as substituent groups, methyl, ethyl, ethanol, propyl, isopropyL'butyl, isobutyl, amyl, isoamyl, benzyl, allyl, crotyl, b-amino ethyl; cyclohexyl and cyclic amino groups such as piperidine and methyl piperidine; aromatic groupssuch as methyl aniline, ethyl aniline, ethyl toluidene and propyl xylidine.

As non-fibrous, transparent, cellulosic pellicles which may be coated in accordance with the present invention any smooth, dense, non-fibrous. water-sensitive, transparent pellicle such as may be obtained by the coagulation and/or regeneration of an aqueous cellulosic 'dispersionis contemplated. Such pelliclesinclude those of regenerated cellulose, glycol cellulose, cellulose glycollic acid, lowly esterifled or lowly etherified cellulose derivatives in which one ester group or one ether group is associated with several cellulose units. 1

Any moistureproofing coating composition of the general type disclosed in the patent to Charch and Prindle Patent No. 1,737,187 or of the type disclosed in U. S. 'A. Patent No. 2,147,629 (Charch) may be used in accordance with the present invention. Such coatings contain a a moistureproofing agent, such as wax, and a filmforming agent such as a cellulose derivative or a resin together with known modifying agents for said coatings, such as blending agents and plasticizers.

The mold inhibiting compounds of this inven tion being non-toxic and non-odorous in the proportionsused, may be safely'applied to coating compositions used in connection with the wrapping tissue for foodstuffs, cigars, toilet articles,

After smoothing and drying, the films coated added. Since, in general, the balance of constituents of a coating composition is very critical in order to combine -a large number of properties such as surface characteristics, moistureproofness, temperature resistance, transparency, etc.,

I it becomes of considerable importance that the addition of an agent to inhibit mold growth will not change any of the large number of factors governing the characteristics of the coating composition. The compositions of this'invention are found eminently satisfactory for this purpose.

Since it is obvious that many changes and modifications can be made in the above-described details, it is to be understood that the invention is not to be limited thereto except as set forth in the following claims.

I claim:

1. A non-fibrous, transparent, moistureproof, cellulosic pellicle suitable for use as wrapping tissue containing incorporated therein, as a mold inhibiting agent, a thiuram sulfide.

2. A non-fibrous, transparent, moistureproof, cellulosic pellicle suitable for use as wrapping tissue containing incorporated therein, as a mold inhibiting agent, 0.1% to 1.0% of an alkyl derivative of a thiuram sulfide.

3. A non-fibrous, transparent, moistureproof cellulosic pellicle suitable for use as wrapping tissue containing incorporated therein, as a mold inhibiting agent, 0.1% to 1.0% of a tetra-alkyl derivative of a thiuram sulfide.

4. A non-fibrous, transparent, moistureproof, cellulosic pellicle suitable for use as wrapping tissue containing incorporated therein, as a mold inhibiting agent, 0.1% to 1.0% of a tetramethyl thiuram sulfide.

5. A non-fibrous, transparent, cellulosic wrapping tissue coated with a moistureproofing composition, said moistureprooflng composition being from the group consisting of cellulose substitution derivative film forming agent-wax and resin film forming agent-wax, and containing incorporated therein, as mold-inhibiting agent, alkyl thiuram sulfide.

a regenerated cellulose sheet coated with a composition consisting of:

Parts Nitrocellulose (12.5% N) 6.70 Damar resin 1.77 Paraflin 0. 50 Dibutyl phthalate 2.80 Tetramethyl thiuram di-sulfid 0. 03

10. A mold resistant, moistureproof, transparent, flexible sheet wrapping material comprising a regenerated cellulose sheet coated with a composition consisting of .Parts Nitrocellulose (12% N) 6.50 Ester gum 2. 93 Dibutyl phthalate 4. Parafiin 0.40 Tetraethyl thiuram di-sulfide 0.07

11. A mold resistant, moistureproof, transpar ent, flexible sheet wrapping material comprising a regenerated cellulose sheet coated with a composition consisting of:

Parts Nitrocellulose (12.5% N) 6.70 Damar resin 1.75 Parafiin' 0.50 Dibutyl phthalate 2.80 Tetramethyl thiuram mono-sulfide 0.05

12. A mold resistant, moistureproof, transparent, flexible sheet wrapping material comprising a cellulosic pellicle coated with a moistureproofing coating composition, said moistureproofing ing coating composition, said moistureproofing 6. A non-fibrous, transparent, cellulosic wrap-.

ping tissue coated with a moistureproofing composition, said moistureproofing composition being from the group consisting of cellulose substitution derivative film forming agent-wax and resin film forming agent-wax, and containing incorporated therein, as a mold inhibiting agent, an alkyl derivative of a thiuram sulfide.

7. A non-fibrous, transparent, cellulosic wrapping tissue coated with a moistureproofing composition, said moistureproofing composition being from the group consisting of cellulose substitution derivative film forming agent-wax and resin film forming agent-wax, and containing incorporated therein, as a mold inhibiting agent, a tetra-alkyl derivative of a thiuram sulfide.

8. A non-fibrous, transparent, cellulosic wrapping tissue coated with a moistureproofing composition, said moistureproofing composition being from the group consisting of cellulose substitution derivative film forming agent-wax and resin film forming agent-wax, and containing incorporated therein, as a mold inhibiting agent, a tetraethyl thiuram sulfide.

9. A mold resistant, moistureproof, transparent, flexible sheet wrapping material comprising coating composition being from the group consisting of cellulose substitution derivative film forming agent-wax and resin film forming agent-wax, and containing 0.3% to 0.5% (based on the solids thereof) tetra methyl thiuram disulfide. 4

14. A mold resistant, moistureproof, transparent, flexible sheet wrapping material comprising a cellulosic pellicle coated with a moistureproofing coating composition, said moistureproofing coating composition being from the group consisting of cellulose substitution derivative film fonning agent-wax and resin film forming agentwax, and containing 0.1% to 0.1% (based on the solids thereof) thiuram sulfide of the formula:

in which .1: represents a positive integer less than 3 and R1, R2, R3 and R4 represent radicals from the group consisting of hydrogen, alkyl and aryl.

15. A moldresistant, moistureproof, transparent, flexible sheet wrapping material comprising a regenerated cellulose sheet coated with a moistureproofing coating'composition, said moistureproofing coating composition being from the group consisting of cellulose substitution derivative film forming agent-wax and resin film forming agent-wax, and containing 0.1% to 1.0% (based on the solids thereof) thiuram sulfide sulfide, dicyclopentyl methylene thiuram di-sul flde, and dicyolopentyl methylene thiuram monosulflde.

16. A non-fibrous, transparent cellulosic wrapping tissue comprising a. celluiosic pelliqle base with a. moistureproonng coating of the cellulose substitution derivative-wax type thereon, the said moistureprooflng coating containing incorporated therein, as a. mold inhibiting agent, an A alkyl derivative of a thiuram sulfide.

WALTER JOHN JEBENS. 

